The present invention relates to a storage apparatus and control method thereof, and, for example, is suitably applied to a storage apparatus that provides data of a snapshot image of an arbitrary generation to a host system.
In recent years, a storage apparatus for managing a snapshot image of a plurality of generations by acquiring a snapshot image of an operational volume at a certain point in time, storing past data (differential data) when data is to be stored in the operational volume and information representing the generation of such snapshot image in a data retention unit after the point in time when such snapshot image is acquired, and reading the read source of data of the snapshot image of the generation to be read by switching it to the operational volume or data retention unit is becoming widely used.
Further, in recent years, as described in Japanese Patent Laid-Open Publication No. 2005-301628 for instance, proposed is a storage apparatus having a control processor for controlling differential data by controlling the reading and writing of data from and into an operational volume created with a storage area of a plurality of disk drives, and controlling the writing of past data stored in the operational volume as differential data per generation in a pool volume, wherein, when the data volume stored in the pool volume exceeds a first prescribed value, the generation of the differential data to be deleted among the differential data written in the pool volume is determined, and the differential data of the determined generation is deleted.
Nevertheless, with the foregoing storage apparatus, since data transmitted from the host system is written in the operational volume, and the data of the snapshot image is read from the operational volume, the access load on the operational volume will increase.
In addition, when acquiring a plurality of snapshot images and reading the data of a plurality of snapshot images from the operational volume as with the foregoing storage apparatus, the access load on the operational volume will increase even more.